Annelid Dissection

Use the following website to help you answer these questions. If you cannot find an answer to a question on this website, search for the answer using any website or your text.

Virtual Dissection : http://biog-101-104.bio.cornell.edu/BioG101_104/tutorials/animals/earthworm.html

External Anatomy

  1. Click on external, dorsal surface (ventral surface down, dorsal surface up). To what phylum does it belong? What is your evidence for that?
  2. Note the difference in coloration. Why is the dorsal surface of the skin darker?
  3. Find the anterior and posterior ends and the clitellum (the wider portion, which is closer to the anterior surface).
  4. Count the number of segments. (How many are there in front of the clitellum? In the clitellum? Behind the clitellum?) ______
  5. Use the following website to answer the next questions.

What do they eat? What does the soft texture of the mouth
say about their diet?______What type of digestive system does it have, (One-Way, or
Two-Way)? ______
Setae are the dark projections on each section. How many
setae are there on each section? What purpose do the setae serve? ______

6. Click on External, Ventral surface of the worm.
a. On which segment is the sperm duct opening? ______What is its

function?______

b.  On which segment is the oviduct opening? What is its function?

______

c. Because it can make both sperm and egg, what do we call this type of

organism?______

d. Given the location of both, is the creature
likely to self-fertilize? ______

e. What type of fertilization does it practice,
internal or external? ______

Internal Anatomy

  1. What do earthworms eat? Given that, what color would you expect the contents of the intestine to be? ______
  2. Click on Internal Morphology 5 images. Look at the parts of the worm that are pinned back. To what body system does the skin belong? Given the earthworm's form of locomotion, what else are you pinning back, and to what body system do they belong? Since the earthworm does not have lungs, what function does the skin serve?______
  3. Identify and diagram the Pharynx & Esophagus. (What is the one function of the two organs? How is their function similar in humans, and how is it different?) ______
  4. Identify and diagram the Gizzard & Crop. (Which of the two is harder? What does that say about its function?) ______
  5. Identify and diagram the Dorsal Blood Vessel and the 5 Aortic Arches. (What role do the arches play in the worm? What is the equivalent organ - be careful here - in humans, and to what body system does it belong? Why do humans have less than five?) ______
  6. Identify and diagram the Seminal Vesicles and the Seminal Receptacles. (What is the function of each? What are the equivalent organs in humans, and to what body system do they belong?) ______
  7. Identify and diagram the Suprapharyngeal Ganglia. (What is its function? What is the equivalent organ in humans, and to what body system does it belong?)______
  8. Now click on Internal morphology, 2 images. Find the Ventral Nerve Cord. Diagram it. (What is its function? What is the equivalent organ in humans, and to what body system does it belong? What aspect of this organ differentiates the earthworm from members of our phylum?) ______